/*
 * ------------------------------------------------------------------------
 *  Copyright by KNIME AG, Zurich, Switzerland
 *  Website: http://www.knime.com; Email: contact@knime.com
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License, Version 3, as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, see <http://www.gnu.org/licenses>.
 *
 *  Additional permission under GNU GPL version 3 section 7:
 *
 *  KNIME interoperates with ECLIPSE solely via ECLIPSE's plug-in APIs.
 *  Hence, KNIME and ECLIPSE are both independent programs and are not
 *  derived from each other. Should, however, the interpretation of the
 *  GNU GPL Version 3 ("License") under any applicable laws result in
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 *  you the additional permission to use and propagate KNIME together with
 *  ECLIPSE with only the license terms in place for ECLIPSE applying to
 *  ECLIPSE and the GNU GPL Version 3 applying for KNIME, provided the
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 *
 *  Additional permission relating to nodes for KNIME that extend the Node
 *  Extension (and in particular that are based on subclasses of NodeModel,
 *  NodeDialog, and NodeView) and that only interoperate with KNIME through
 *  standard APIs ("Nodes"):
 *  Nodes are deemed to be separate and independent programs and to not be
 *  covered works.  Notwithstanding anything to the contrary in the
 *  License, the License does not apply to Nodes, you are not required to
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 *  prepare and propagate Nodes, in each case even if such Nodes are
 *  propagated with or for interoperation with KNIME.  The owner of a Node
 *  may freely choose the license terms applicable to such Node, including
 *  when such Node is propagated with or for interoperation with KNIME.
 * -------------------------------------------------------------------
 *
 */
package org.knime.base.node.mine.svm.kernel;

import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * This class is responsible for managing all the kernels that are known
 * to the SVM.
 *
 * @author Stefan Ciobaca, University of Konstanz
 * @author Nicolas Cebron, University of Konstanz
 */
public final class KernelFactory {

    /**
     * The different kernel types.
     *
     * @author cebron, University of Konstanz
     */
    public enum KernelType {
        /** Polynomial Kernel. */
        Polynomial,
        /** Hypertangent Kernel. */
        HyperTangent,
        /** Radial Basis Function Kernel. */
        RBF
    }
    /* Map with all known kernels */
    private Map<KernelType, Kernel> m_kernels;

    /* The singleton instance. */
    private static KernelFactory instance = null;

    /*
     * Constructor of the kernel factory. If someone wants to add a kernel,
     * this is what needs to be modified (and the getType function).
     */
    private KernelFactory() {
        m_kernels = new LinkedHashMap<KernelType, Kernel>();
        m_kernels.put(KernelType.Polynomial, new PolynomialKernel());
        m_kernels.put(KernelType.HyperTangent, new HyperTangentKernel());
        m_kernels.put(KernelType.RBF, new RBFKernel());
    }

    /**
     * Return a default kernel.
     * @return KernelType
     */
    public static KernelType getDefaultKernelType() {
        assureInstance();
        return KernelType.valueOf(getKernelNames()[1]);
    }

    /**
     * Given a pointer to a kernel, get its type.
     * If you modify this function, don't forget the constructor.
     * @param kernel instance
     * @return kernel name
     */
    public static KernelType getType(final Kernel kernel) {
        if (kernel.getClass().getSimpleName().equals("PolynomialKernel")) {
            return KernelType.Polynomial;
        }
        if (kernel.getClass().getSimpleName().equals("HyperTangentKernel")) {
            return KernelType.HyperTangent;
        }
        if (kernel.getClass().getSimpleName().equals("RBFKernel")) {
            return KernelType.RBF;
        }
        assert false : "Trying to get name of unknown kernel type";
        return null;
    }

    /*
     * Make sure the singleton instance has been created.
     */
    private static void assureInstance() {
        if (instance == null) {
            instance = new KernelFactory();
        }
    }

    /**
     * Returns a kernel given by its name.
     * @param kerneltype the type of the Kernel
     * @return the requested kernel
     */
    public static Kernel getKernel(final KernelType kerneltype) {
        assureInstance();
        return instance.m_kernels.get(kerneltype);
    }

    /**
     * Returns all the kernels known by this factory.
     * @return the array of kernel names
     */
    public static String [] getKernelNames() {
        assureInstance();
        String [] names = new String [instance.m_kernels.keySet().size()];
        int counter = 0;
        for (KernelType k : instance.m_kernels.keySet()) {
            names[counter] = k.name();
            counter++;
        }
        Arrays.sort(names);
        return names;
    }

    /**
     * For each kernel, look at the number of parameters it requires, and
     * return the highest.
     * @return the maximal number of parameters from any of the kernels
     */
    public static int getMaximalParameters() {
        int result = 0;
        for (KernelType type : KernelType.values()) {
            if (getKernel(type).getNumberParameters() > result) {
                result = getKernel(type).getNumberParameters();
            }
        }
        return result;
    }
}
